code: def start(self):
      if self.subapp is None:
          print(
              "No subcommand specified. Must specify one of: %s"
              % (self.subcommands.keys())
          )
          print()
          self.print_description()
          self.print_subcommands()
          self.exit(1)
      else:
          return self.subapp.start()
  
imports: import os
  from traitlets.config.application import Application
  from IPython.core.application import BaseIPythonApplication, base_flags
  from IPython.core.profiledir import ProfileDir
  from IPython.utils.importstring import import_item
  from IPython.paths import get_ipython_dir, get_ipython_package_dir
  from traitlets import Unicode, Bool, Dict, observe
label_desc: Use image node_id 1 for calling the ProfileApp obj's underlying member method code with example usage: obj.start() and returns: self